Generally, turbine rotor assemblies include a rotor wheel to which a plurality of blades are coupled. The blades extend radially outward from a platform that extends between an airfoil portion of the blade and a dovetail portion of the blade. The dovetail portion of the blade has at least one pair of dovetail tangs that couples the rotor blade to a complimentary dovetail slot in an outer rim of a rotor wheel.
Dovetail slots in the outer rim of the rotor wheel are sized to receive the dovetail tangs of the dovetail portion of the blade. These blades receive cooling air from a circumferential slot that intersect with the dovetail. Portions of the dovetail slots where the cooling slot intersects can have high stress regions. Mitigating stress can extend the usable fatigue life of the rotor wheel. The stress is caused by a combination of mechanical cyclic loads and thermal cyclic and static loads which can result in the accumulation of strain over time. The stress can be mitigated by complex processes that can include disassembling components for repair, using robotic heads, and/or using five-axis machines. These processes can suffer from drawbacks that they are expensive, are not widely available, involve complex tooling, and result in the rotor wheel being out of service for a long period of time.
Other techniques include using a manual grinding operation to remove fatigued material from the dovetail. However, these uncontrolled processes may introduce undesired high stress concentrations into the dovetail, which may result in reducing the component life capability.
In yet another technique, material may be removed in a concentrated stress region using a controlled break edge method. This method uses a customized edge grinder to follow the contours of the slot edge. Though the shape and consistency of the edge break helps the part meet the intended service life, this method does not significantly reduce the stress nor remove enough strained material to significantly extend the operating life of the feature.
A process of machining a turbine rotor wheel, a repair tool for machining a turbine rotor wheel, and a turbine rotor wheel that do not suffer from the above drawbacks would be desirable in the art.